Probably should tap the brakes on getting the car if you're relying on a tax refund to finance it. Remember, tax refunds aren't a good thing in most cases...

Also scary you need your "tax lady" to give you the good news and you sound like you have no earthly idea what the number will be.

I pretty much know exactly what I'll owe before I even start.

I have never owed. I wind up getting a good refund every year. Everyone I work with is the same way, save a few guys who have jumped tax brackets due to having second jobs.
I know the minimum I'll get, but I don't know what I'll get from the refi and the other car purchase. That's where the uncertainty is. I don't know the first thing about doing taxes since I have a tax lady for that. I always wind up paying out a lot more in taxes throughout the year, and every tax season is like Christmas for us (myself and my coworkers).
I can get the car whenever I want, but a better return means I can get it with a lot lower payment. I want a lower payment, and I'd prefer to not have to wait until summer to get the same payment. My current 2003 Mazda beater car that I intentionally drove into the ground is on it's last leg, and I'm not sure it'll hold out until summer. There are squeaks, rattles and grinding noises that I can't identify, and the car is rusting out at 170k salt-pounded miles.